Prosthetic devices, generally known as tissue expanders, are implanted in the body to restore shapes and contours that have been surgically altered or accidentally deformed. These devices usually require periodic infusion or withdrawal of fluid to maintain or achieve the desired shape of the prosthesis or to vary the volume of fluid within the prosthesis for the purpose of establishing proper tension to the prosthesis.
Rather than inject the fluid directly into a prosthesis it has been found beneficial to infuse the fluid into a fluid transfer device, occasionally referred to as a septum, which directs the fluid into the prosthesis. These transfer devices or septums, which facilitate the administration of fluid to an interconnected prosthesis are usually implanted below the skin in the vicinity of the prosthesis. Each device is typically connected to the prosthesis by a fill tube.
One type of subcutaneously implanted septum includes a chamber with a dome shaped elastomeric cover and a rigid flat base. The cover provides a needle-penetrable member to infuse liquid into the chamber. A needle is directed through the patient's skin where it accesses the chamber through the cover. When the needle is withdrawn, the cover self-seals so as to prevent fluid leakage from the chamber. The rigid base acts as a needle stop so as to prevent the needle from penetrating entirely through the device and into the patient's body. It is highly desirable to have a septum with a chamber that is easy to access without fear of having the needle passing through the device.
Occasionally, a septum will twist or even flip over after implantation in a patient. This happens especially in obese patients where the skin and tissue that surround the septum are somewhat soft and loose. The twisting occurs when torque is applied to the septum that exceeds the skin and tissue forces which hold the septum in its desired orientation. Known ways of reducing the undesirable movement of the septum include widening the flat base and suturing the septum in place.
Once a septum has twisted, the fill chamber is no longer easily accessible by a needle since the dome is no longer easy to locate and penetrate. Furthermore, twisting of a septum connected to a prosthesis can kink the fill tube preventing fluid from being infused into or withdrawn from the prosthesis.
It is an object of the present invention to provide a septum that is easily accessible for fluid infusion and for fluid withdrawal even when the septum has twisted within the patient.
It is a further object of the present invention to provide a septum that has a substantial needle-penetrable surface area for its size so as to facilitate ease of needle accessibility to the fluid chamber.
It is also an object to reduce the possibility of needle penetrating through the septum into the patient's body while facilitating ease of needle accessibility to the fluid chamber.
It is also considered desirable to accomplish these objectives while reducing the possibility of kinking the fill tube connecting the septum to the prosthesis.